RAMDISK 설정
# fdisk -l /dev/ram0
Disk /dev/ram0: 67 MB, 67108864 bytes
255 heads, 63 sectors/track, 8 cylinders, total 131072 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

# vim /etc/default/grub
...........................
### 5GB ###
GRUB_CMDLINE_LINUX="brd.rd_size=5120000"

# update-grub
# reboot
# fdisk -l /dev/ram0
Disk /dev/ram0: 4194 MB, 4194304000 bytes
255 heads, 63 sectors/track, 509 cylinders, total 8192000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/ram0 doesn't contain a valid partition table


RAMDISK JOURNAL  변경
# stop ceph-osd-all
# ceph-osd --flush-journal -i 2
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0d 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0d 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
2016-08-19 16:13:00.206457 7f56c0c22940 -1 flushed journal /var/lib/ceph/osd/ceph-2/journal for object store /var/lib/ceph/osd/ceph-2

# ceph-osd --mkjournal -i 2
 HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device
2016-08-19 16:15:34.230426 7f1612de3940 -1 journal read_header error decoding journal header
 HDIO_DRIVE_CMD(identify) failed: Inappropriate ioctl for device
2016-08-19 16:15:34.233372 7f1612de3940 -1 created new journal /var/lib/ceph/osd/ceph-2/journal for object store /var/lib/ceph/osd/ceph-2


# rm -rf /var/lib/ceph/osd/ceph-2/journal
# ln -s /dev/ram0 /var/lib/ceph/osd/ceph-2/journal
# chown -h ceph:ceph /var/lib/ceph/osd/ceph-2/journal
# chown ceph:ceph /dev/ram0
# start ceph-osd-all-starter